Exam 2: Cranial Nerves Flashcards
Function of the cranial nerves
A. The cranial nerves function to bring in sensory information from facial/neck regions and send out motor commands
- Dorsal for sensory nuclei and ventral for motor nuclei in both the spinal cord and brainstem cranial nerves
- THE INNERvation is bilateral
WHich nerves have cell bodies in the forebrain?
olfactory and optic
I, II
Which nerve has cell bodies in the cervical spinal cord?
spinal accessory (XI)
WHICH nerves have cell bodies in the midbrain?
ocular motor and trochlear
III, IV
Which nerves have cell bodies in the pons?
trigeminal, abducens, facial, vestibulocochlear (V, VI, VII, VIII)
trigeminal and vestibulocochlear have medulla components
WHich nerves have cell bodies in the medulla?
glossopharyngeal, vagus, hypoglossal (IX, X, XII)
WHIch nerves are purely sensory in function
CN I, II, VIII
olfactory, optic, vestibulocochlear
Which nerves are purely motor in function?
CN III, IV, VI, XI, XII
ocular motor, trochlear, abducens, spinal accessary, hypoglossal
WHich nerves are mixed sensory and motor?
CN V, VII, IX, X
trigeminal, facial, glossopharyngeal, vagus
CN I - the olfactory nerve
function: smell, somatic sensory
cell bodies: CNS, Primary sensory neurons detects olfactory information in the neuroepithelium in the upper nasal cavities and synapse onto neurons in the olfactory bulb. These neurons make up the olfactory nerve
- After forming olfactory tracts (aka nerves) in the olfactory bulb, the axons synapse onto neurons in the piriform cortex adjacent to the temporal lobe
CN II - the optic nerve
function: vision, purely sensory
cell bodies: Retinal ganglion cells in the retina of the eye send their axons, as part of the optic nerve, into the lateral genicukate nucleus of the thalamus
- After synapsing onto neurons in the thalamus, the thalamic neurons then go to the primary visual cortex in the occipital lobe
CN III - the oculomotor nerve
function: eye movement, motor only, autonomic and somatic
cell bodies: nuclei for nerve in midbrain
- Contain somatic motor axons (voluntary control, aka lower motor neuron) and parasympathetic axons for pupillary constriction reflexes and ciliary muscles for near vision
CN IV - the trochlear nerve
- function: eye movement downwards
- nuclei for the nerve in midbrain
- This nerve is purely somatic motor (voluntary control, aka lower motor neuron)
CN VI - the abducens
- function: lateral movement of the eyes
- nuclei for the nerve in the pons
- purely somatic motor
CN V - the trigeminal nerve sensory
- function: sensory innervation (touch, pain) of the face (and dura) and motor control of muscles for mastication, which is called the branchial motor root/ touch and pain for face)
- Nuclei for the nerve: in ventrolateral pons. CN V primary sensory neurons synapse onto these nuclei
- 1st neuron: primary sensory neuron
2nd neuron: - Chief trigeminal nucleus in pons – for crude touch (medial lemniscus)
- Spinal trigeminal nucleus in pons/medulla-for pain (trigeminothalamic)
- Both sends axons to ventral posterior medial nucleus (VPM) in thalamus
- From the VPM thalamus for both tracts, the thalamic neuron then sends its axons to the primary somatosensory cortex
CN V - the trigeminal nerve motor
- The trigeminal motor nuclei contains the lower motor neuron (or second neuron) that will innervate the mastication muscles—in the pons
- An upper motor neuron from the primary motor cortex (primarily) sends its axons down bilaterally to the trigeminal motor nuclei
CN VII - the facial nerve
- Function: the main function is to control muscles of facial expression, other functions include tears and salivation and taste (autonomic and somatic)
- Nuclei: facial nerve nucleus in the pons
- Components: visceral motor (branchial), parasympathetic motor and sensory and visceral and somatic sensory
- There is ipsilateral and contralateral control
CN VIII – the vestibulocochlear nerve
- Function: hearing and vestibular sensation
- Nuclei: cochlear nucleus in the pons/medulla junction for hearing and the vestibular nuclei in the pons/medulla
- Components: somatic sensory only
a. A primary sensory neuron that innervates the cochlea sends its axons to the cochlear nucleus
b. The cell bodies of these sensory neurons ( for hearing) are the spiral ganglia - 1st neuron=primary sensory neuron in its own ganglia
- 2nd neuron=cochlear or vestibular nuclei (pons/medulla)
- 3rd neuron = thalamus
medial geniculate for hearing
Ventral posterior for vestibular
CN IX – the glossopharyngeal nerve
- autonomic and
- Function: main function is sensation in the posterior tongue and pharynx (touch, pain and temperature)
- Nuclei: each component will have its own nuclei in the brainstem-most nuclei are within the medulla
- Components: parasympathetic, somatic sensory and visceral motor, visceral sensory
CN X – the vagus nerve
- Function: swallowing, voice box, taste in specific regions, heart/lungs/GI tract autonomic innervation
- Nuclei: each component will have its own nuclei in the brainstem-most nuclei are within the medulla
- Components: parasympathetic, somatic and visceral sensory and visceral motor (branchial)
CN XI - the spinal accessory nerve
CN XI is purely visceral motor and helps head move. Motor axons travel with CN X vagus so CN XI is considered functionally a part of the vagus. Nuclei are within cervical spinal cord, however
CN XII - the hypoglossal nerve
- Function: intrinsic movement of the tongue
- Nuclei: the hypoglossal nucleus in the medulla
- Components: somatic motor
